A fatal fairground accident

Int. J. Fatigue Vol. 20, No. 2, pp. 169–173, 1998 1998 Elsevier Science Ltd. All rights reserved

Printed in Great Britain0142–1123/98/$19.00+.00

PII: S0142-1123(97)00103-5

A fatal fairground accident

L. P. Pook

Department of Mechanical Engineering, University College London, TorringtonPlace, London WC1E 7JE, UK

On 26 December 1978 one arm of a fairground machine known as the ‘Concorde Flyer’ installed atthe Kelvin Hall, Glasgow, Scotland, fractured due to fatigue. The car attached to the arm overturned,killing two passengers. A description of the events leading up to the accident, and the cause of thefailure, are taken from the report of an official inquiry. After the event the immediate cause of theaccident became obvious and it is easy to see how it could have been prevented. There were noprosecutions for criminal negligence, and the question of civil liability for damages appears to havebeen settled out of court. 1998 Elsevier Science Ltd.

(Keywords: product liability; inspection techniques; failure analysis; welded joints)

INTRODUCTION

On Boxing Day (26 December) 1978 one arm of afairground machine known as the ‘Concorde Flyer’installed indoors at the Kelvin Hall, Glasgow, Scotland,fractured. The car attached to the arm overturned,killing two passengers1. Where structural failure dueto fatigue or other causes leads to a catastrophe societyas a whole takes an interest2,3. The reactions of anadvanced society, through its institutions, follow welldefined lines. An inquiry is set up to ascertain thecauses of the accident, including any failure to followestablished procedures. Inquiries usually reveal a situ-ation where a number of errors and omissions, eachnon-critical in itself, have linked up into a chain ofcoincidence which has resulted in catastrophe2.

This particular accident was selected as an exampleof a catastrophic fatigue failure for several reasons.The structure involved was relatively simple, and asfar as those immediately concerned, the accident wascompletely unexpected. After the event the immediatecause of the acident became obvious. An officialinquiry, whose report1 is a matter of public record,was held. This report is the source of much of thematerial presented here.

The paper was originally written as a chapter for abook4 published in 1983, as an example of a cata-strophic fatigue failure, but was not included for legalreasons. A shorter version5, with less emphasis onlegal aspects, was published in 1990.

LEGAL BACKGROUND

Scotland is part of the UK but has a separate legalsystem. An inquiry into the accident was held underthe Fatal Accidents and Sudden Deaths (Scotland) Act1976 before Sheriff J. Irvine Smith. In Scotland a

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Sheriff is a judge who presides over a local courtknown as a Sheriff Court. Under the Act a Sheriff sitsalone, and the authorities can call for a court inquirywhen a fatal accident ‘has occurred under circum-stances such as to give rise to serious public concern’.The Court is required to establish the facts concerningthe accident, but not to apportion blame in either acriminal or a civil sense. Apart from findings of factthe Act also makes provision for recommendations tobe made in appropriate circumstances. Some rec-ommendations (the Recommendations) were includedin the report of the Inquiry. This report1 is the sourceof most of the material presented in this paper.

Under the Glasgow Corporation Consolidation Gen-eral Powers Order Confirmation Act 1960 a licence isrequired from the Licensing Committee of GlasgowDistrict Council to operate a machine such as theConcorde Flyer within Glasgow. A machine isinspected on behalf of the Council before a licenceis issued.

In 1976, following several fairground accidents, theUK Government issued a ‘Guide to safety at fairs’6

(the Guide). Its introduction notes that ‘The guide doesnot try to take account of the many individual vari-ations in premises and amusement devices that are tobe found. It is intended, rather, as an indication of thestandards to be aimed at’. The Guide is referred to inthe report of the Inquiry. Safety certificates as pre-scribed by the Guide are a requirement of the Show-men’s Guild (a trade association of fairgroundoperators). These certificates cover structural, mechan-ical and electrical safety.

The Inquiry was lengthy. The transcript of the Courtproceedings covered some 910 pages, and was sup-plemented by voluminous productions, including Refs6 and 7. The evidence presented to the Court was, on

170 L. P. Pook

many issues, conflicting, contradictory and confused.While the Court had the benefit of expert witnessesthe written report was produced by the Sheriff alone,without the assistance of expert assessors.

THE CONCORDE FLYER

The Concorde Flyer, also known as the ski-jump sys-tem machine, was intended to give passengers a ‘thrill’similar to that of a ski-jump. In the course of use themachine was frequently dismantled and re-asembled asit was moved to different fairgrounds about the country.It was owned and operated by Mr Joseph White,designed by Mr Rainer Wolfe, a qualified mechanicalengineer and manufactured by George Maxwell andSon of Musselburgh, well known manufacturers offairground equipment.

The machine (Figure 1) consisted of ten cars eachrigidly attached to an individual arm, which in turnwas attached by pivots to a central hub. The cars ranin an anticlockwise direction on a circular track. Eachcar had seating for four passengers, and was fittedwith a single wheel with a rubber tyre. Each arm wasa welded assembly,ca 0.5 m wide, made from lowcarbon structural steel. Originally an arm consisted of100 × 50 mm rectangular hollow sections along theleading and trailing edges, cross-braced by 50 mmsquare hollow sections. The hub was driven by anelecric motor fitted with appropriate control gear. Thetrack wasca 9 m in diameter, and incorporated a largeand a small hill. The normal speed of operation was8–9 r.p.m.

The Concorde Flyer was first commissioned aboutMarch 1976. Between this time and the time of theaccident various defects appeared in the machine, andvarious repairs were carried out. It was not possible

Figure 1 Schematic top view of Concorde Flyer showing one arm


to establish the precise sequence of defects appearingin the machine, nor the precise nature or dates ofrepairs carried out. This is contrary to the Guide andalso to the Recommendations, both of which requirethat appropriate records be kept. The history of themachine is outlined later in this paper.

Soon after the machine was first commissioned itgave some trouble, and modified parts for the pivotswere supplied by the manufacturers.

At about the end of 1976 at least one of the armsfractured. As a result the owner contacted the manufac-turer (George Maxwell and Son) and Mr John Rennieof Renald Engineering. Repairs were carried out underthe supervision of Mr Rennie, but the exact nature ofthe damage and repairs is uncertain.

The owner continued to be dissatisfied with themachine, and complained to the manufacturer. AboutDecember 1977 the manufacturer asked the designer(Mr Wolfe) to plan modifications. These includedshortening the arms byca 0.6 m (to a length ofca3 m) compensating for this by extending the centralhub, and modifying the pivots attaching the arms tothe hub. These modifications were completed early in1978, and the machine was recommissioned aboutEaster 1978.

Soon after an arm fractured, and the owner instructeda local engineering firm to carry out repairs. Theyapparently welded a metal splint to the fractured arm.

Subsequently the owner arranged for all the arms tobe strengthened. It is not clear whether this was onhis own initiative or in consultation with Mr Rennie.Modifications to strengthen the arms in the vicinity ofthe pivots consisted of welded on cover plates. As aresult the arm was now a boxed in structure in thisarea (Figure 2), in contrast to the original more opendesign. Attachments at the hub were also altered, and

Figure 2 Top view of arm in vicinity of failure (welds not shown)

171A fatal fairground accident

angle irons welded to parts of the leading and trailingedges. The designer of the machine (Mr Wolfe) wasnot consulted about these modifications, and he wasnot aware that they carried out. This is contrary toboth the Guide and the Recommendations.

FAILURE ANALYSIS

The accident to the Concorde Flyer occurred on 26December 1978. The machine was boarded, and startedup. When it was about to start its third revolution, andbefore it had reached its full speed, the arm attachedto one car fractured near the hub. After the accidenta failure analysis7 was carried out by the Research andLaboratory Services Division of the Health and SafetyExecutive, a UK Government agency.

At the time of the accident structural details in thevicinity of the failure (Figure 2) were as follows. Apivot box consisting of 100 mm square hollow sectionhad 38 mm thick end plates welded on. A 63 mmdiameter pivot passed through the end plates, and wasfillet welded to the inner face of one of the end plates.The ends of the pivots engaged in bushes on thecentral hub. Each of the 100× 50 mm rectangularsections along the leading and trailing edges of thearm was fillet welded to the pivot box along threesides. The fourth, outer, side had a 100× 6 mm plateattached by longitudinal fillet welds. This side platewas in turn attached to the pivot box by a fillet weld.This partial penetration weld resulted in a severe notch.This notch (Figure 3) was perpendicular to the fatiguestresses induced in the arms as the cars were forceduphill and ran downhill. It was not visible externally.A 6.2 mm thick top and a 5.1 mm thick bottom plate,atached by fillet welds, completed the assembly.

Detailed examination7 showed that the fracture originwas at the leading edge of the arm. A fatigue crackhad initiated at the partial penetration weld attachingthe side plate to the pivot box (Figure 3) and grownthrough the weld over a period of, probably, months.It had then grown into the welds attaching the top andbottom plates to the arm. The fatigue crack reached acritical size, and the rest of the fracture was ductiletearing of the top and bottom plates and the trailingedge welds, completely severing the arm (Figure 2),probably in a single continuous action.

Figure 3 Section through initial fatigue crack


The fatigue crack was not visible externally until ithad grown right through the weld. The fatigue crackhad reached the outside of the weld so as to beobvious on visual examination, to anyone with relevantexperience, for some time before the accident. Thiswas clear from the degree of contamination of thefracture surfaces.

Further cracks, visible to the naked eye on externalexamination, were found on the arm that failed, andon five further arms. One of the cracks had beenpainted over, and paint had penetrated the crack.Another crack was at the trailing edge of an arm inthe location corresponding to the origin of the crackwhich caused the accident.

Detailed laboratory examination of two of the otherarms revealed the presence of fatigue cracks in threeof the four locations corresponding to the fatigue crackwhich caused the accident. These cracks had not pen-etrated to the surface so were not visible externally.

SAFETY CERTIFICATES

At the time of the accident, three safety certificates,certifying that the Concorde Flyer had been indepen-dently inspected, were in force. Two were issued onbehalf of the Showmen’s Guild, and were in the formrecommended by the Guide. The third was a ‘Licencefor a Public Show’ issued by Glasgow District Councilunder the Glasgow Corporation Consolidation GeneralPowers Order Confirmation Act 1960. Further, theowner had carried out a daily visual inspection inaccordance with requirements of the Guide.

In March 1978 Mr Rennie, who had been appointedby the Showmen’s Guild as an inspector, issued asafety certificate for the Concorde Flyer. This statedthat he had inspected the machine with regard to itsstructural and mechanical safety, and was of the opi-nion that its condition was such that it did not presenta danger to the public. The certificate further statedthat as part of this examination he observed a fullyloaded test run. The certificate issued by Mr Renniedid not satisfy the requirements of the Guide. He didnot possess the professional qualifications prescribedby the Guide. He was not independent, since he hadpreviously supervised work on the machine (above).The machine was not examined during a fully loadedtest run. The emergency braking system, prescribed bythe Guide, was not working at the time of the inspec-tion. He did not clean any parts of the machine beforeinspection. The Sheriff commented ‘That certificatewas admittedly not worth the paper it was writen on’.

A further certificate, issued in May 1978 by anotherinspector appointed by the Showmen’s Guild, statedthat the machine had been examined for the purposesof electrical safety and had been found safe.

About November 1978 the Concorde Flyer wasexamined by three inspectors appointed by Mr Welsh,the Deputy Director of Building Control of GlasgowDistrict Council. They inspected the machine visually,but did not remove grease or dirt. They did not observeany cracks or other defects, and they did not considerthe modifications made to the machine would affectthe question of safety. Accordingly, they recommendedthe machine as safe for use. As a result of theirrecommendations, a Licence for a Public Show wasissued in December 1978. Mr Welsh considered that

172 L. P. Pook

the inspection was directed at ‘the siting and the buildup of the machine…not an inspection of the machineitself, just the way it had been erected’, and that theinspection ‘did not extend to any defects on themachine, for which they had seen a Showmen’s Guildcertificate’. The inspection cannot be regarded as satis-factory.

Apart from the inspections carried out there wasfurther opportunity for cracks to be noticed each timethe machine was dismantled for transport andreassembled at another fairground. The evidencepresented to the Inquiry revealed a situation which was,to say the least, disturbing. One lawyer commented that‘everyone was leaving it to everyone else’.

DISCUSSION

As far as those immediately involved were concernedthe accident was completely unexpected. After theaccident the immediate cause of the accident becameobvious. This was a fatigue failure from a welded jointwhose design was poor from a fatigue viewpoint, andwas in a region where the bending moment in theplane of the arm was high. The Inquiry revealed anumber of errors and omissions, and during its coursedamaging allegations were made against various peopleinvolved with the Concorde Flyer. It is perhaps surpris-ing that there were no prosecutions for criminal negli-gence. Prosecutions would have been possible underthe Health and Safety at Work Act and, had therebeen sufficient evidence, would have been initiated bythe Procurator Fiscal. The question of civil liability fordamages is believed to have been settled out of court,so no comment is possible.

The report of the Inquiry did not address the questionof why the earlier fractures in the arms did not leadto a catastrophic failure. These earlier fractures werealmost certainly due to fatigue. The original design ofthe arms could be expected to be redundant in thatductile tearing from a fatigue crack in the vicinity ofthe pivot box would lead to fracture of only one ofthe 100 × 50 mm rectangular hollow sections whichformed the leading and trailing edge of an arm. Sucha failure would not be catastrophic, and would beobvious to the machine operator. This probablyexplains why earlier failures were merely an expensivenuisance. By contrast, the boxed in structure of thearm that failed (Figure 2) would not be redundant inthat ductile tearing would be more likely to lead to acomplete failure9.

Another point which was not addressed by the reportof the Inquiry is that the overall design of the ConcordeFlyer was not redundant. Each car was supported byonly one wheel, so that the car attached to an armwould become unstable if its arm fractured.

A sequence of events where repeated, but unsuccess-ful, attempts are made to strengthen welded structuresagainst fatigue by welding on additional material isoften observed. The practice has been repeatedlydenounced by fatigue specialists, for example, Ref. 8.In this particular case the end result of repeated repairswas that the detail design in the vicinity of the fractureorigin was poor from a fatigue viewpoint.

The Inquiry into the accident revealed a situationwhere a number of errors and omissions, each non-


critical in itself, had linked up into a chain of coinci-dence which resulted in catastrophe. Such ‘systemsfailures’ are a common feature of a wide range ofcatastrophic failures2. The chain of coincidence whichled to the accident to the Concorde Flyer may besummarized as follows. Modifications, not approvedby the original designer, were made to the arms of themachine. Poor detail design of the modificationsresulted in the development of potentially dangerousfatigue cracks. Inspections of the machine on behalfof regulatory authorities did not reveal the presence ofthese fatigue cracks. Poor detail design of the modifi-cations resulted in complete fracture of an arm byductile tearing from a fatigue crack which had reacheda critical size. After the fracture of an arm the carattached to it was unstable, and consequently overturn-ed.

With the benefit of hindsight it is easy to see howthe accident could have been prevented. In particular,inspections were clearly inadequate in that they did notreveal the presence of easily visible cracks. However, itis possible that cracks were noticed, but either theirsignificance was not appreciated, or it was hoped thatthey would not lead to serious trouble since earlierfractures had merely been an expensive nuisance. Whatappears to be perverse refusal to heed signs of impend-ing trouble has been a contributary factor in numer-ous catastrophes10.

The Recommendations included in the report of theInquiry amplified requirements of the Guide, with theintention of preventing future similar accidents. Therewas emphasis on the need for adequate records, andfor inspections to be carried out by independent, pro-fessionally qualified persons. One of the Recommen-dations is of particular interest, and is reproducedbelow verbatim.

Where a machine like the Concorde Flyer for useby the public on a fairground or amusement centreor the like is manufactured, it should not be allowedto go into use unless a licence of safety and soundconstruction has been granted in respect of it by apublic body or persons approved thereby, such asthe Health and Safety Executive, who have given ita thorough inspection on its completion and underworking conditions. The examination should be ofthe rigorous standard to which aircraft are subjectedbefore they are allowed into service.

The reference to aircraft practice is interesting in thatthe Sheriff regarded this as the best available. Whilephilosophies of design against fatigue4 are similar,details are different because of the very different struc-ture, materials and load histories involved. In aircraftpractice extensive use is made of full-scale testing inorder to assess fatigue resistance. This would probablybe prohibitively expensive for a machine such as theConcorde Flyer, which would either be a ‘one-off’, orat most made in very limited numbers. As weight isrelatively unimportant it would be better to rely on aconservative approach to design stresses.

It is clearly difficult to devise procedures to preventa recurrence of this type of accident. Any practical

173A fatal fairground accident

solution must take into account legal, technical andeconomic factors.

CONCLUSIONS

1. The immediate cause of the accident to the Con-corde Flyer was a fatigue crack which originated ina welded joint.

2. The overall cause of the accident was a number oferrors and omissions, each non-critical in itself,which linked up into a catastrophic chain of coinci-dence.

3. It is perhaps surprising that there were no pros-ecutions for criminal negligence. The question ofcivil liability for damages appears to have beensettled out of court, so no comment is possible.

4. Practical procedures to prevent a recurrence of thistype of accident, must take into account legal, tech-nical and economic factors.


REFERENCES

1 Irvine Smith, J.,Report of Inquiry into the Death of ThomasJohn McDonald and Clare McDonald. Sheriff Clerk’s CriminalOffice, Glasgow, 1980.

2 Bignall, V. F., Peters, G. and Pym, C.,Catastrophic Failures.Open University Press, Milton Keynes, 1977.

3 Rosmanith, H. P. (Ed.),Structural Failure, Product Liabilityand Technical Insurance. Elsevier Science, Amsterdam, 1984.

4 Pook, L. P.The Role of Crack Growth in Metal Fatigue. MetalsSociety, London, 1983.

5 Pook, L. P., The Kelvin Hall fairground accident.Strain, 1990,26(3), 113–115.

6 HMSO, Guide to Safety at Fairs. HMSO, London, 1976.7 Nicholson, C. E. and Towers, R. T.,Examination of a Compo-

nent from a Fairground Amusement Device. Health and SafetyExecutive, Sheffield, 1979.

8 Gurney, T. R.,Fatigue of Welded Structures, 2nd edn. Cam-bridge University Press, Cambridge, 1979.

9 Boyd, G. M. (Ed.),Brittle Fracture in Steel Structures. But-terworths, London, 1970.

10 Kennet, F., The Great Disasters of the Twentieth Century.Marshall Cavendish, London, 1975.

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A fatal fairground accident